Pressure sores are nerve malnutrition and blood circulation disorder caused by long-term pressure or long-term physical and chemical stimulus on local body tissues. Continuous ischemia, anoxia, and malnutrition of the local tissues cause the skin to lose normal functions and lead to festering and necrosis of soft tissues. For instance, sustained vertical pressure, or shear and friction on local tissues may cause pressure sores, and usually, pressure sores are caused by two to three joint forces.
Pressure sores, which are not primary diseases but belong to common clinical complications, are injuries caused by other primary diseases without good care. Pressure sores not only bring considerable physical and mental sufferings and economic burden to the patients but also increase the workload of nurses, and even worse, may lead to secondary infection and trigger septicemia, hence becoming life-threatening.
Most pressure sores can be prevented. However, in practical cases of illness, moisture, heat, age, and obesity all significantly increase the incidence of pressure sores. Therefore, people use various methods to prevent pressure sores. At present, division-type air rings, pressure sores prevention cold liquid cushions or other composite cushions are mainly used to prevent pressure sores, but all these products are flawed in that the cushion continuously exerts pressure on the body, and cannot maintain a stable shell temperature.
In addition, as shown in FIG. 1A and FIG. 1B, US Patent Publication No. 5052068 discloses a contoured cushion, in which a plurality of air cells is disposed on a flexible base 2 thereof. The air cells include a short cell 4, an intermediate cell 6, and a long cell 8 that are organized into an outer zone x and an inner zone y; the air cells of the outer zone x are in communication with each other, the air cells of the inner zone y are in communication with each other, but the air cells of the outer zone x are not in communication with the air cells of the inner zone y. Once the user settles into the cushion, he opens the valves 42 and 44 respectively in communication with the outer zone x and the inner zone y to release the pressure in the air cells of the inner zone x and the outer zone y, thereby adjusting the height of each air cells in the zones, so as to be more in conformance with the shape of human buttocks on the cushion and; hence, the user gets the most comfortable sitting posture and experience.
Moreover, as shown in FIG. 2A and FIG. 2B, US Patent Publication No. 5502855 discloses a cellular cushion, in which a plurality of air cells are disposed on a base 2 thereof. The air cells are organized into four zones, namely, r, s, t, and u; air cells in each zone are in communication, and the four zones can be communicated through a manifold 24. Moreover, communication among the four zones can be cut off by closing separate air ducts 20, 21, 22, and 23. Before the cushion is used, the air cells in the zones are inflated by means of an inflating air valve 26, and at this time, the clip-type hose valve 30 is open, that is, the r, s, t, and u zones are in communication through the manifold 24. After sufficient air is charged into the cushion, the inflating air valve 26 is closed. Then, the user sits on the cushion, and air is slowly released through the inflating air valve 26. As the air is being released, the buttocks of the user sink into the air cells, and when reaching a desired sinking depth, the user closes the inflating air valve 26. In addition, the user can close the separate air ducts 20, 21, 22, and 23 so as to prevent air from flowing among the four zones. This patent has similar advantages as the patent described above, i.e., the user can release air so that the cushion conforms to the shape of body very well, thereby obtaining the most comfortable sitting posture and experience.
When used by those who need to keep a sitting posture for a long time, the cushions in the above two patents can provide very comfortable sitting posture and experience, however pressure is applied to the body continuously, and pressure sores are still very likely to occur.